1. Field of the Invention
The present invention relates to an optical scanning unit of a position measuring system for measuring the relative position of a first machine element with respect to a second machine element in at least one measuring direction. The present invention furthermore relates to a method for mounting a position measuring system, wherein the position measuring system is designed for measuring the relative position of a first machine element with respect to a second machine element in at least one measuring direction.
2. Discussion of Related Art
An optical scanning unit is known from EP 0 548 848 A1, for example. The scanning unit includes a support for a scanning grating and a detector unit with an arrangement of several photo-detectors. The support of the scanning grating and the detector unit are rigidly connected with each other. The position of the photo-detectors in relation to the scanning grating is predetermined and fixed by this connection. In this state the support of the scanning grating and the detector unit are installed as a common structural unit on a machine element to be measured.
In order to design the scanning unit for easy handling, the structural size, and therefore the stability, of this structural unit is greatly limited. As a rule, the detector unit is connected via cables to external electronic elements. These cable connections can exert impermissible forces on the detector unit, which are transmitted through the connection and therefore can lead to bending, and therefore distortion of the scanning grating.
In connection with highly accurate position measuring systems it can furthermore be necessary to assign a cooling device to the detector unit in order to prevent impermissible heat radiation from the detector unit to its surroundings, i.e. the scanning grating and the scale. Forces which can lead to bending or distortions of the scanning grating can also be introduced by this cooling device.